Solid-state imaging device, production method and drive method thereof, and camera

ABSTRACT

A solid-state imaging device capable of reducing an eclipse (blocking) of an incident light at a circumferential portion of a light receiving portion and realizing a larger angle of view and high-speed driving. A single-layer transfer electrode configuration of forming first transfer electrodes and second transfer electrodes by one polysilicon layer is adopted. Two shunt wirings extending in a horizontal direction are formed on the first transfer electrodes connected in a horizontal direction and, for example, four-phase transfer pulses are supplied to first transfer electrodes and second transfer electrodes on transfer channels through low-resistance shunt wirings extending in the horizontal direction.

RELATED APPLICATION DATA

This application is a divisional of U.S. patent application Ser. No.11/179,963, filed Jul. 12, 2005, the entirety of which is incorporatedherein by reference to the extent permitted by law. The presentinvention claims priority to Japanese Patent Application No. 2004-221981filed in the Japanese Patent Office on Jul. 29, 2004, the entirety ofwhich also is incorporated by reference herein to the extent permittedby law.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a camera, a solid-state imaging deviceused therefor such as a charge coupled device (CCD) type solid-stateimaging device, and a method thereof.

2. Description of the Related Art

To achieve a larger angle of view and transfer at a high-speed rate of aCCD solid-state imaging device, there are demanded a lowering aresistance of transfer electrode. It is because such the transferelectrode is generally composed as a distributed constant circuit of anRC, and a high resistance of the transfer electrode will result innon-sharpness (dulling) and delay of a transfer pulse applied by thetransfer electrode to disturb a transfer of CCD charges. Then, transferelectrodes and wiring bus lines have been made to be low resistance.

A technique of attaining a low-resistance transfer electrode is that,for example, when the transfer electrode is composed of polysilicon, animpurity is introduced to polysilicon to make the resistance low.Alternately, the polysilicon is made to be a thick film to obtain alow-resistance sheet. In those cases, it is expected an improvement upto only several tens of percentage both in the thickness and theresistance.

As another method of attaining a low-resistance transfer electrode,there is also known a method of using material having a low resistancefor the transfer electrode instead of polysilicon. As the material to beused, tungsten silicide (WSi) is well known. In the case used WSi, theresistance is expected to become lower by about one digit.

For the case where the resistance has to be lowered by more than onedigit, there has been proposed a configuration of forming a transferelectrode of the CCD itself by polysilicon and using material having alower resistance than that of above explained WSi, such as aluminum, asa shunt wiring (for example, refer to the following publications:Japanese Patent No. 3123068, Japanese Unexamined Patent Publication No.7-283387, Japanese Unexamined Patent Publication No. 7-226496, JapaneseUnexamined Patent Publication No. 8-236743, and Japanese UnexaminedPatent Publication No. 2003-60819).

Actually, most of the techniques so far have applied a method ofproviding a shunt wiring along a vertical transfer CCD. Such the shuntwiring in the vertical direction suffers from the disadvantages that thetransfer mode is limited and multi-phase driving used for interleavingtransfer of pixels is hard to be realized.

Furthermore, a configuration of connecting transfer electrodes made bypolysilicon over several pixels in the crossing direction becomes alsonecessary. Although a sufficient thickness of polysilicon has to besecured and the polysilicon itself has to have a low resistance, forexample, for performing high-speed driving, work of making pixels finerhas a trade-off relationship with work of making the polysilicon filmthicker. It is because when the polysilicon film becomes thicker, aheight of light shading mask to be formed thereon becomes high, so thateclipse of light (meaning that a light to be irradiated on pixels isblocked by a light shading mask) becomes large when pixels become finer.

A CCD solid-state imaging device with finer pixels has been developedbesides realization of a larger angle of view thereof, and a size of onepixel has become 2 μm or so nowadays. Although there are variouschallenges in realizing finer pixels, to maintain and improve sensitivecharacteristics is the most significant one.

In this case, since an aperture area of a light receiving portion isreduced due to the miniaturization of pixels, it is required theconfiguration of an upper layer portion of pixels, such as an on-chiplens, has to be optimized to improve the focusing property. However, anincident light to the light receiving portion is blocked by the transferelectrode itself, so that there has been a proposal of reducing athickness and projections of the transfer electrode.

As a proposal for reducing the projections, instead of the vertical CCDconfiguration of forming a transfer electrode by two or three layers ofpolysilicon, a single-layer transfer electrode configuration of formingthe same by one polysilicone layer has been proposed (for example, referto Japanese Unexamined Patent Publication No. 2003-60819).

However, the circumstances are that a CCD with a larger angle of viewand a CCD with high-speed transfer, etc. are actually hard to berealized only by the well-known single-layer transfer electrodeconfiguration, and an eclipse of an incident light cannot besufficiently reduced.

SUMMARY OF THE INVENTION

It is desired to provide a solid-state imaging device for reducingblocking of an incident light at a circumferential portion of a lightreceiving portion and attaining a larger angle of view and high-speeddriving.

According to the present invention, there is provided a solid-stateimaging device, including a plurality of light receiving portionsarranged in a first direction and a second direction perpendicular tothe first direction; a plurality of transfer channels extending in thesecond direction, each being arranged between the neighboring lightreceiving portions; a plurality of first transfer electrodes arranged onthe transfer channels, the neighboring first transfer electrodespositioned at both sides of the light receiving portion being connectedin the first direction; a plurality of second transfer electrodesarranged in the same layer of the first transfer electrodes, on thetransfer channel; and low-resistance wirings of which the numbercorresponds to the number of transfer electrodes, extending over thefirst transfer electrode in the first direction, and having a lowerresistance than those of the first transfer electrodes and the secondtransfer electrodes, each of the low-resistance wirings being connectedto the first transfer electrode and the second transfer electrode oneach transfer channel through a connecting portion.

In the solid-state imaging device of the present invention as above, atransfer pulse can be transferred to the first transfer electrodes andthe second transfer electrodes on the transfer channels vialow-resistance wirings, so that non-sharpness (dulling) and delay of thetransfer pulse can be prevented.

Also, the transfer pulse can be transmitted via the low-resistancewiring, a film thickness of the first transfer electrode and the secondtransfer electrode can be made thin. Consequently, heights of the firsttransfer electrode, the second transfer electrode and low-resistancewiring at the circumferential portion of the light receiving portion canbe made low.

According to the solid-state imaging device of the present invention, itis possible to reduce an eclipse (blocking) of an incident light at thecircumferential portion of the light receiving portions, and a largerangle of view and high-speed driving can be achieved.

Preferably, the solid-state imaging device may include a light shadingmask arranged on the first transfer electrodes, the second transferelectrodes and the low-resistance wirings in a state of interpolating aninsulation film, the light shading mask forming a plurality of openingsfor the light receiving portions.

According to the present invention, there is provided the solid-stateimaging device, including the steps of: forming the plurality of lightreceiving portions in the first direction and the second direction;forming the transfer channels extending in the second directionarranging each of the transfer channel between the neighboring lightreceiving portions; and forming the first transfer electrodes on thetransfer channels, the neighboring first channels positioned at bothsides of the light receiving portion being connected in the firstdirection, and forming the second transfer electrodes on the transferchannels in the same layer of the first transfer electrodes.

According to the present invention, there is provided driving method ofthe solid-state imaging device, for driving by four-phase driving thesolid-state imaging device.

Preferably, the solid-state imaging device may include third transferelectrodes arranged on the same layer of the first transfer electrodesand the second transfer electrodes, on the transfer channels in thefirst direction; three low-resistance wirings being arranged byextending over the first transfer electrodes in the first direction, andeach of the three low-resistance wirings being connected to the firsttransfer electrodes, the second transfer electrodes and third transferelectrodes on the transfer channels by a connecting portion.

There is provided a method of producing the solid-state imaging devicefurther including a step of forming third transfer electrodes on thetransfer channels, in a layer formed by the same steps of forming thefirst transfer electrodes and the second transfer electrodes.

According to the present invention, there is provided a driving methodof the solid-state imaging device, for driving by a three-phase drivingor a six-phase driving a solid-state imaging device.

According to the present invention, there is provided a camera,including: an optical lens; and the solid-state imaging device forconverting an image obtained through the optical lens to an electricsignal.

BRIEF DESCRIPTION OF DRAWINGS

These and other objects and features of the present invention willbecome clearer from the following description of the preferredembodiments given with reference to the attached drawings, in which:

FIG. 1 is a view of the basic configuration of a camera according to anembodiment of the present invention;

FIG. 2 is a plan view of a key part of a pixel portion in a solid-stateimaging device according to a first embodiment;

FIG. 3A is a sectional view along a line A-A′ in FIG. 2, and FIG. 3A isa sectional view along a line B-B′ in FIG. 2;

FIG. 4 is a sectional view of a step of producing the solid-stateimaging device according to the first embodiment;

FIG. 5 is a sectional view of a step of producing the solid-stateimaging device according to the first embodiment;

FIG. 6 is a sectional view of a step of producing the solid-stateimaging device according to the first embodiment;

FIG. 7 is a sectional view of a step of producing the solid-stateimaging device according to the first embodiment; and

FIG. 8 is a plan view of a key part of a pixel portion in a solid-stateimaging device according to a second embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Below, preferred embodiments of a camera and a solid-state imagingdevice used therefor and a method of producing the same of the presentinvention will be explained with reference to the drawings.

First Embodiment FIG. 1 is a schematic view of a camera of an embodimentof the present invention.

The camera shown in FIG. 1 includes an optical lens system 41, acharge-coupled device (CCD) 42, a CCD driver 43 and a signal processor44.

The optical lens system 41 may include an objective lens, and anautomatic-focusing and/or automatic exposure adjusting lens andmechanism. In the embodiment, the optical lens system 41 may include ashutter and a stop. The optical lens system 41 receives a light of animage and outputs the same to the CCD 42 to be focused thereat.

The CCD 42 and the CCD driver 43 cooperate to convert the incident lightto the CCD 42 to an electric signal.

The signal processor 44 receives the converted electric signalindicating the image and carries out the image processing to recover theimage, for example. Details of the CCD 42 and CCD driver 43 will bedescribed.

As an example of the CCD 42 shown in FIG. 1, a four-phase drivingoperation is performed by cooperation of the CCD 42 and the CCD driver43, which will be explained later on. A four-phase driving CCD will beexplained as an example in the present embodiment.

FIG. 2 is a plan view of a main portion of a pixel portion of asolid-state imaging device, as an example of the CCD 42 in FIG. 1,according to the present embodiment. In the present embodiment, afour-phase driving CCD will be explained as an example. The CCD 42 andthe CCD driver 43 cooperate to perform the four-phase drive operation,described later.

In the pixel portion, light receiving portions 1 composing a pixel arearranged. A plurality of the light receiving portions are arranged in ahorizontal direction H and in a vertical direction V, not illustrated.The light receiving portion 1 is composed of a photodiode, generates asignal charge in accordance with an incident light quantity andaccumulates for a certain period.

Transfer channels 2 extending in the vertical direction are arrangedadjacent to the light receiving portions in the horizontal direction.The transfer channel 2 is provided to extend between light receivingportions 1 arranged in the horizontal direction. The transfer channel 2generates a distributed potential for transferring signal charges in thevertical direction V.

A transfer electrode 3 is arranged on the transfer channel 2 extendingin the vertical direction V. The transfer electrode 3 is divided into afirst transfer electrode 3 a and a second transfer electrode 3 b in theview of a layout shape. Note that when it is not necessary to separatethe first transfer electrode 3 a from second transfer electrode 3 b,they are simply referred to as the transfer electrode 3. In the presentembodiment, a single-layer transfer electrode configuration is applied,wherein the first transfer electrode 3 a and the second transferelectrode 3 b are formed in the same layer. The transfer layer 3 isformed, for example, by polysilicon. It is preferable that the transferelectrode 3 has a thin film thickness of, for example, 200 nm or thinnerto prevent an eclipse of the incident light.

The above first transfer electrode 3 a and the second transfer electrode3 b are alternately and repeatedly arranged in the vertical direction inthe transfer channel 2. The transfer electrodes 3 and the transferchannels 2 explained above compose a so-called vertical transfer portionarranged in common for each line of the light receiving portions 1arranged in the vertical direction.

The first transfer electrodes 3 a are connected in the horizontaldirection H by extending between light receiving portions 1 arranged inthe vertical direction. When composing a pixel of 2 μm×2 μm or so, awidth W1 of a part of the first transfer electrode 3 a between the lightreceiving portions 1 is 0.45 μm or so.

Each second transfer electrode 3 b is isolated on the transfer channel2, that is, separated and not connected in the horizontal direction H.The second transfer electrodes 3 b are arranged adjacent to the lightreceiving portion 1.

Two shunt wirings 4 extending in the horizontal direction H are arrangedin the first transfer electrode 3 a over an insulation film. The shuntwirings 4 are formed by tungsten having a lower resistance than that ofpolysilicon forming the transfer electrode 3. The shunt wirings 4correspond to the low-resistance wirings of the present invention. Thenumber of the shunt wirings 4 corresponds to the number of the transferelectrodes arranged for one light receiving portion 1 and is two in thepresent embodiment. A width W2 of one shunt wiring is, for example, 0.12μm, and a width W3 between the two shunt wirings is, for example, 0.16μm. The shunt wirings 4 are divided into shunt wirings 4 a and shuntwirings 4 b depending on a destination of the connection. Note that whenit is not necessary to separate the shunt wiring 4 a from the shuntwiring 4 b, it will be simply referred to as a shunt wiring 4.

The shunt wiring 4 a is connected to the first transfer electrodes 3 aby connecting portions 5 on the transfer channel 2. The shunt wiring 4 bis connected to the second transfer electrodes 3 b by connectingportions 5 on the transfer channel 2.

The first transfer electrodes 3 a and the second transfer electrodes 3 balternately and repeatedly arranged on the transfer channel 2 in thevertical direction V are supplied with transfer pulses of four phaseshaving different phases øV1, øV2, øV3 and øV4 along the verticaldirection through the shunt wirings 4. The voltage of the transferpulses øV1 to øV4 are, for example, −7V to 0V.

In addition to the transfer pulses øV1 and øV3, the floating type secondtransfer electrodes 3 b adjacent to the light receiving portion 1 aresupplied with a read-out pulse oR for transferring signal chargesaccumulated in the light receiving portion 1 to the transfer channels 2through the shunt wirings 4 b. The voltage of the read-out pulse øR is,for example +12V to +15V.

FIG. 3A is a sectional view along the line A-A′ in FIG. 2, and FIG. 3Bis a sectional view along the line B-B′ in FIG. 2. Note that theconfiguration of an upper layer portion above the light shading mask 6is shown in FIG. 3A, while that is omitted in FIG. 3B for simplifyingthe drawing.

In the present embodiment, a semiconductor substrate 10, for example,made of n-type silicon is used. In the semiconductor substrate 10, ap-type well 11 is formed. In the p-type well 1, an n-type region 12 isformed, and a p-type region 13 is formed at a position closer to thesurface side than the position of the n-type region 12. A photodiodeformed by the pn-junction of the n-type region 12 and the p-type well 11composes the light receiving portion 1. As a result, the p-type region13 is formed closer to the surface side comparing with the n-type region12, a buried photodiode having a reduced dark current is formed.

A p-type well 14 is formed adjacent to the n-type region 12, and thetransfer channel 2 formed by an n-type region is formed in the p-typewell 14. A p-type channel stop portion 16 for preventing flowing ofsignal charges between adjacent light receiving portions 1 is formed. Inthe illustrated example, between the light receiving portion 1 and thetransfer channel 2 on the left side of the light receiving portion 1becomes a reading gate portion 17. Accordingly, the transfer electrode 3controls a potential distribution of the reading gate portion 17, andsignal charges of the light receiving portion 1 is read by the transferchannel 2 on the left side.

In the semiconductor substrate 10 formed with a variety of semiconductorregions, transfer electrodes 3 made by polysilicon are formed via a gateinsulation film 20. A film thickness of the transfer electrode 3 is, forexample, 0.1 μm.

An insulation film 21, for example, made of oxide silicon is formed tocover the transfer electrodes 3. In the transfer electrodes 3, shuntwirings 4, for example, made of tungsten are formed via the insulationfilm 21. A film thickness of the shunt wirings 4 is, for example, 0.1μm. The insulation film 21 is formed with apertures at connectingportions 5, and the shunt wirings 4 and the transfer electrodes 3 areconnected at the connecting portions 5.

An interlayer insulation film 22, for example, made of oxide silicon isformed to cover the shunt wirings 4. A light shading mask 6 for coveringthe transfer electrodes 3 and the shunt wirings 4 is formed via theinsulation film 21 and the interlayer insulation film 22. The lightshading mask 6 is formed with opening portions 6 a above the lightreceiving portions 1.

An interlayer insulation film 23, for example, made of phosphosilicateglass (PSG) or borophosphosilicate glass (BPSG) film is formed to coverallover the light shading mask 6, and thus the surface is flattened.

On the interlayer insulation film 23, an inner-layer lens, for example,made of oxide silicon or nitride silicon is formed, and a flatteningfilm 25 is formed further thereon. The flattening film 25 is, forexample, formed of a resin having a high light transmittance to avisible light.

On the flattening film 25, a plurality of kinds of color filters 26 fortransmitting lights in predetermined wavelength regions are formed. Thecolor filters 26 are colored to be any of red (R), green (G) and blue(B) as primary colors and, for example, any of yellow (Ye), cyan (Cy),magenta (M) and green (G), etc. as complementary colors.

On the color filters 26, an on-chip lens 27 is formed. The on-chip lens27 is formed by a light transmitting material, such as a negativephotosensitive resin.

Next, an operation of the solid-state imaging device according to theabove embodiment will be explained.

An incident light is converged by the on-chip lens 27, and only a lightin a predetermined wavelength range transmits because of the colorfilter 26. The light transmitted through the color filter 26 is furthercollected by the inner-layer lens 24 and guided to the light receivingportion 1.

When the light of the image, for example, is irradiated to the lightreceiving portion 1, signal charges (electrons in the present example)in accordance with the incident light quantity are generated byphotoelectric conversion and accumulated for a certain period in then-type region 12 of the light receiving portion 1. When the read-outpulse øR is supplied to the second transfer electrodes 4 b (refer toFIG. 2) through the shunt wirings 4 b, a potential distribution of theread-out gate portion 17 changes and signal charges in the n-type region12 are read out to the transfer channel 2.

After the signal charges are read out to the transfer channel 2, thefour-phase transfer pulses øV1 to øV4 are supplied to the transferelectrodes 3 arranged in the vertical direction V via the shunt wirings4. The potential distribution of the transfer channel 2 is controlled bythe four-phase transfer pulses øV1 to øV4, and then the signal chargesare transferred in the vertical direction V.

While not illustrated, after the signal charges are transferred in thevertical direction V, they are transferred in the horizontal directionby a horizontal transfer portion, converted to a voltage in accordancewith a signal charge amount thereof by an outputting portion and output.

Next, a method of producing the solid-state imaging device according tothe present embodiment explained above will be explained with referenceto sectional views of steps in FIG. 4 to FIG. 7. The sectional views ofsteps in FIG. 4 to FIG. 7 are sectional views corresponding to FIG. 3A.

As shown in FIG. 4A, in the semiconductor substrate 10 formed by n-typesilicon, the p-type well 11, n-type region 12, p-type region 13, n-typetransfer channels 2, p-type wells 14 and p-type channel stop portions 16are formed by the ion implantation method. Note that the ionimplantation may be performed in a state where an oxide silicon film,etc. is formed on the semiconductor substrate 10. When forming an oxidesilicon film, etc., it is removed after the ion implantation.

Next, as shown in FIG. 4B, the gate insulation film 20, for example,formed of oxide silicon is formed on the semiconductor substrate 10 bythe thermal oxidization method or chemical vapor deposition (CVD)method. Continuously, on the gate insulation film 20, polysilicon isdeposited by the CVD method and processed by dry etching, so that thetransfer electrodes 3 are formed. Note that a polysilicon film thicknessis preferably 200 nm or thinner in the case of a pixel of 2 μm×2 μm toreduce an eclipse of light.

Next, as shown in FIG. 5A, the insulation film 21 formed by oxidesilicon, etc. for covering the transfer electrodes 3 is formed by theCVD method. Continuously, the insulation film 21 at positions to beconnecting portions 5 is removed, so that the transfer electrodes 3 arepartially exposed on (or above) the transfer channel 2.

Next, as shown in FIG. 5B, for example, a tungsten film is formed on theinsulation films 21 by the sputtering method or CVD method, and thetungsten film is processed by the dry etching, so that shunt wirings 4are formed.

Next, as shown in FIG. 6A, oxide silicon films, etc. are deposited bythe CVD method, so that interlayer insulation films 22 for covering thetransfer electrodes 3 and the shunt wirings 4 are formed.

Next, as shown in FIG. 6B, a tungsten film is formed by the sputteringmethod or CVD method, the tungsten film is processed by the dry etchingto cover the transfer electrode 3 and shunt wiring 4, so that the lightshading mask 6 having an opening portion 6 a on (or above) the lightreceiving portion 1 is formed.

Next, as shown in FIG. 7A, a BPSG film or a PSG film is deposited by theCVD method to form the interlayer insulation film 23. After thedeposition, by performing reflow processing, a surface of the interlayerinsulation film 23 becomes flattened. In the reflow processing, thetemperature becomes high as 800° C. or higher, so that it is configuredto be resistive to a high temperature by not using aluminum but usingtungsten for the shunt wirings 4 and light shading mask 6.

Next, as shown in FIG. 7B, above the light receiving portion 1, theinner-layer lens 24 is formed on the interlayer insulation film 23. Forforming the inner-layer lens 24, a light transmitting film of oxidesilicon or nitride silicon, etc. is deposited, for example, by theplasma CVD method first, then, a resist film having a convex lens shapeis formed by the resist film application, patterning and reflowprocessing, and finally, by performing etching under a condition thatetching selectivity of the resist film and the light transmitting filmbecomes approximately 1, the inner-layer lens 24 is formed. Afterforming the inner-layer lens 24, the flattening film 25, for example,made of a resin having a high light transmittance to a visible light isformed.

As the following steps, the color filters are formed, for example, by astaining method. Then, a light transmitting resin, such as a negativephotosensitive resin, is deposited on the color filters 26, and etchingusing as a mask a resist pattern having a convex lens shape is performedin the same way as in the inner-layer lens 24 so as to form the on-chiplens 27. From the above steps, the solid-state imaging device accordingto the present embodiment is produced.

Next, an effect of the solid-state imaging device according to thepresent embodiment explained above will be explained.

In the present embodiment, a single-layer transfer electrodeconfiguration of forming the first transfer electrodes 3 a and thesecond transfer electrodes 3 b by one polysilicon layer is applied.Then, on the first transfer electrodes 3 a connected in the horizontaldirection, the two shunt wirings 4 a and 4 b extending in the horizontaldirection are formed and connected to the first transfer electrodes 3 aand the second transfer electrodes 3 b on the transfer channels 2.

Since the four-phase transfer pulses øV1 to øV4 can be supplied to thefirst transfer electrodes 3 a and the second transfer electrodes 3 b onthe transfer channels 2 via the low-resistance shunt wirings 4 a and 4 bextending in the horizontal direction, it is possible to reducenon-sharpness (dulling) and delay of the transfer pulses. As a result,it is possible to realize a larger angle of view and high-speed driving.

Also, since the transfer pulses are supplied to all transfer electrodes3 of the pixel portion by the shunt wirings 4 a and 4 b, the transferelectrodes 3 having the single-layer configuration do not have to be farlow resistance, so that it may be made thinner comparing with that inthe case of the related art. Also, since tungsten composing the shuntwirings 4 a and 4 b has a lower resistance than that of polysilicon bytwo order (digits) or so, they can be made thinner. For example, thetransfer electrodes 3 and the shunt wirings 4 may be made thin as 200 nmor thinner, respectively. Consequently, a height of the light shadingmask 6 covering the transfer electrodes 3 and shunt wirings 4 andsurrounding the light receiving portion 1 can be lowered, so that aneclipse of the incident light by the light shading mask 6 can bereduced.

Also, since the shunt wirings 4 a and 4 b extend in the horizontaldirection, the shunt wirings 4 a and 4 b are connected to all the firsttransfer electrodes 3 a or all the second transfer electrodes 3 barranged in the horizontal direction on the transfer channels 2.Therefore, the transfer mode is not limited and it is possible torespond to interleaving transfer of pixels, etc.

Furthermore, since the first transfer electrodes 3 a are provided underthe shunt wirings 4 a and 4 b extending in the horizontal direction,when the read-out pulse oR is supplied to the floating type secondtransfer electrodes 3 b through the shunt wirings 4 b, the potentialdistribution of the semiconductor substrate 10 under the shunt wirings 4b is not affected due to the blocking effect by the first transferelectrodes 3 a as the lower layer. Therefore, color mixture phenomenonbetween light receiving portions 1 arranged in the vertical directioncan be prevented.

Second Embodiment

An example of the four-phase driving CCD was explained in the firstembodiment, while in the present embodiment, an example of a six-phasedriving or three-phase driving CCD, wherein the CCD 42 and the CCDdriver 43 cooperate for performing three-phase driving, will beexplained. FIG. 8 is a plan view of a main part of a pixel portion in asolid-state imaging device according to the second embodiment. Note thatthe same reference numbers are given to the same components as those inFIG. 2 and explanations thereof will be omitted.

In the transfer channel 2 extending in the vertical direction V, thetransfer electrodes 3 made by single-layer polysilicon are arranged. Inthe present embodiment, the transfer electrodes 3 includes thirdtransfer electrodes 3 c in addition to the first transfer electrodes 3 aand the second transfer electrodes 3 b. A film thickness of the transferelectrodes 3 is preferably thin as, for example, 200 nm or thinner toprevent an eclipse of an incident light.

The first transfer electrodes 3 a, the second transfer electrodes 3 band the third transfer electrodes 3 c are alternately and repeatedlyarrange in the vertical direction on the transfer channels 2. Thetransfer electrodes 3 and the transfer channels 2 compose a so-calledvertical transfer portion arranged in common for each line of the lightreceiving portions 1 arranged in the vertical direction V.

The first transfer electrodes 3 a are connected in the horizontaldirection H by extending between the light receiving portions 1 arrangedin the vertical direction, and each of the second transfer electrode 3 bhas an isolated shape on the transfer channel 2, that is, it is notconnected in the horizontal direction H and has a separated shape, whichare the same as those in the first embodiment.

The third transfer electrode 3 c also have an isolated shape on thetransfer channel 2, that is, not connected in the horizontal direction Hand have a separated shape in the same way as the second transferelectrode 3 b. The third transfer electrodes 3 c are arranged adjacentto the light receiving portion 1.

In the transfer electrodes 3 a, three shunt wirings 4 extending in thehorizontal direction H are formed via an insulation film. The shuntwirings 4 are formed by tungsten having a lower resistance than that ofpolysilicon composing the transfer electrodes 3 and correspond to thelow-resistance wirings of the present invention. The shunt wirings 4include three kinds of shunt wirings 4 a, 4 b and 4 c.

The shunt wirings 4 a are connected to the first transfer electrodes 3 aby connecting portions 5 on the transfer channels 2. The shunt wirings 4b are connected to the second transfer electrodes 3 b by connectingportions 5 on the transfer channels 2. The shunt wirings 4 c areconnected to the third transfer electrodes 3 c by connecting portions 5on the transfer channels 2.

When realizing six-phase driving, six-phase transfer pulses øV1, øV2,øV3, øV4, øV5 and øV6 having different phases are supplied along thevertical direction to the first transfer electrodes 3 a, the secondtransfer electrodes 3 b and the third transfer electrodes 3 c arrangedalternately and repeatedly in the vertical direction V via the shuntwirings 4 on the transfer channels 2. Among them, a read-out pulse øR issupplied to the two transfer electrodes 3 b and 3 c adjacent to a pixelthrough the shunt wirings 4 b and 4 c.

When realizing three-phase driving, the three-phase transfer pulses øV1,øV2 and øV3 having different phases are supplied along the verticaldirection to the first transfer electrodes 3 a, the second transferelectrodes 3 b and the third transfer electrodes 3 c are arrangedalternately and repeatedly in the vertical direction V via the shuntwirings 4 on the transfer channels 2. Among them, the read-out pulse øRis supplied, for example, to one of third transfer electrode 3 cadjacent to a pixel through the shunt wirings 4 c.

As explained above, by adding the floating type third transfer electrode3 c and providing the three shunt wirings extending on the firsttransfer electrodes 3 a, the three-phase driving or the six-phasedriving of the solid-state imaging device can be realized.

The solid-state imaging device according to the present embodiment hasthe same effects as those in the first embodiment.

The present invention is not limited to the above explanation on theembodiments.

For example, in the above embodiments, examples of the three-phasedriving, four-phase driving and six-phase driving were explained, buttwo-phase driving may be also achieved. In the case of the two-phasedriving, a layout of the transfer electrodes 3 and shunt wirings 4 isthe same as that in the first embodiment. The two-phase driving can berealized by changing the transfer pulses ø3 to ø1 and ø4 to ø2, and bygiving potential gradient to the transfer channel 2 under the transferelectrodes 3 a and 3 b. Also, more than six-phase driving may be alsorealized. In this case, it can be realized only by adding floating typetransfer electrodes and increasing the number of shunt wirings.

Furthermore, the solid-state imaging device of the present invention canbe also applied to an interline transfer type solid-state imaging deviceand a frame interline transfer type solid-state imaging device. Avariety of modifications of the present invention may be made on theconfiguration of upper layers of the light shading mask 6. The valuesand materials, etc, mentioned in the above embodiments are just examplesand the present invention is not limited to those.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alternations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1. A camera, comprising: an optical lens; and a solid-state imagingdevice for converting an image obtained through the optical lens to anelectric signal, said solid-state imaging device comprising: a pluralityof light receiving portions arranged in a first direction and a seconddirection perpendicular to the first direction; a plurality of transferchannels extending in the second direction, each being arranged betweenthe neighboring light receiving portions; a plurality of first transferelectrodes arranged on said transfer channels, the neighboring firsttransfer electrodes positioned at both sides of the light receivingportion being connected in the first direction; a plurality of secondtransfer electrodes arranged in the same layer of said first transferelectrodes, on said transfer channel; and low-resistance wirings ofwhich the number corresponds to the number of transfer electrodes,extending over said first transfer electrode in the first direction, andhaving a lower resistance than those of said first transfer electrodesand said second transfer electrodes, each of said low-resistance wiringsbeing connected to the first transfer electrode and the second transferelectrode on each transfer channel through a connecting portion.
 2. Acamera as set forth in claim 1, wherein each of said second transferelectrodes on said transfer channels is arranged separately.
 3. A cameraas set forth in claim 1, wherein said first transfer electrodes aresupplied with a read-out voltage for reading signal charges accumulatedin said light receiving portion out to the transfer channels throughsaid low-resistance wiring.
 4. A camera as set forth in claim 1, whereinsaid solid-state imaging device comprises a light shading mask arrangedon said first transfer electrodes, said second transfer electrodes andsaid low-resistance wirings in a state of interpolating an insulationfilm, and said light shading mask forming a plurality of openings forsaid light receiving portions.
 5. A camera as set forth in claim 1,wherein said solid-state imaging device comprises third transferelectrodes arranged on the same layer of said first transfer electrodesand said second transfer electrodes, on said transfer channels in thefirst direction, and wherein three low-resistance wirings are arrangedby extending over said first transfer electrodes in the first direction,and each of said three low-resistance wirings is connected to said firsttransfer electrodes, said second transfer electrodes and third transferelectrodes on said transfer channels by the connecting portion.